The Saikyō Line (埼京線) is a service run by East Japan Railway Company (JR East). It runs from Ōsaki station in Shinagawa ward, Tokyo, through Shinjuku, Ikebukuro, Akabane and Musashi-Urawa, to Ōmiya station in Saitama City.
History
In the 1970s, Japanese National Railways (JNR, 国鉄) could not add enough capacity for the growing population around Tokyo. Commuting was so crowded that it was called 'commuter hell' (通勤地獄). JNR added tracks and longer trains. It also split freight and passenger trains between Akabane and Ōmiya on the Tohoku Main Line (東北本線). Demand kept rising outside Tokyo, so the Tohoku and Takasaki lines needed more capacity. Construction of the Tohoku and Joetsu Shinkansen began after approval on 1 October 1971. Residents near the line formed a movement against the Shinkansen. The first plan was to put the Saitama section underground. In March 1973 that was judged too hard because of ground problems, and an elevated line with a commuter line alongside was offered instead. Saitama Prefecture refused the elevated plan, because noise from the Tokaido and Sanyo Shinkansen had already caused protests. Later, JNR promised noise measures and announced the commuter line. The local towns then agreed to the Shinkansen, on condition that the commuter line was built with it.
In November 1978, JNR applied to build the commuter line from Akabane to Miyahara, a length of 22.0 km. It was approved in December 1978. Work began with a ceremony in Toda City on 27 February 1982. The plan had 10 stations between Akabane and Ōmiya. Most of the route was elevated, with a tunnel near Akabane-dai and an underground section at Ōmiya. Musashi-Urawa, where the Musashino Line (武蔵野線) joins, had two platform faces and four tracks so that fast and local trains could pass each other. At first the plan was to run trains from Miyahara on the Takasaki Line (高崎線) through to Shinjuku. Buying land near Musashi-Urawa for a depot was hard, and opposition arose near Miyahara. The depot was built near Minami-Koya station instead, as the Kawagoe depot (now Kawagoe Rolling Stock Center). The Kawagoe Line (川越線), then not electrified, was electrified too, because the population along it kept growing. The Ōmiya to Miyahara section was cancelled. Through trains from the Takasaki Line to Shinjuku were later run after JR was formed, using the Tohoku-Yamanote freight line. That route later became the Shonan-Shinjuku Line (湘南新宿ライン). On 26 July 1984, a steel girder fell while being lifted at a construction site between Kita-Yono and Ōmiya. It hit a passing car, and two people had minor injuries.
On 11 July 1985, JNR announced the name Saikyō for the line. The line opened on 30 September 1985. The 18.0 km branch of the Tohoku Main Line ran from Akabane through Musashi-Urawa to Ōmiya. Together with the Akabane Line from Ikebukuro, trains ran from Ikebukuro to Ōmiya. Some trains also ran through to Kawagoe on the Kawagoe Line, which was electrified from Ōmiya to Komagawa the same day. The fastest express took 44 minutes from Ikebukuro to Kawagoe. Before the line opened, the trip took 69 minutes with a change at Akabane or Ōmiya. All trains used the 103 series. Service had three levels: commuter express (weekday rush hours only), rapid and local trains. On the first day, the PRC automatic route control system had a fault and disrupted timetables. Noise from the 103 series between Akabane and Ōmiya drew complaints. On 3 March 1986 the line was extended to Shinjuku over the Yamanote Freight Line (山手貨物線). Shinjuku ward and local business groups had asked for the extension since 1980. Shibuya ward (1981) and Meguro ward (1982) asked for further extensions. The aim was to ease crowding on the Yamanote Line (山手線) between Ikebukuro and Shinjuku. In the rush hours, all trains ran to or from Shinjuku.
On 1 April 1987, JNR was split up and the line passed to East Japan Railway Company (JR East). Its trains kept the 103 series. Noise on the Akabane to Ōmiya section, and the need to replace old trains on other lines, led JR East to bring in 205 series trains from 1 July 1989. All Saikyō trains used the 205 series from 1 December 1990. The 205 series had a deeper green band on the body. The 103 series had a yellow-green colour like the Yamanote Line. The new traction motors were quieter than those of the 103 series. On 16 March 1996 the line was extended over the freight line to Ebisu. There was one new platform each at Shibuya and Ebisu. The aim was to ease crowding on the Yamanote Line between Shinjuku and Shibuya. The effect was large. Crowding on the Yamanote between Yoyogi and Harajuku fell, which Japanese Wikipedia says had a similar effect to adding two more tracks to the Yamanote Line. Trains from Ebisu could not turn back there, so they ran empty to Ōsaki to reverse. Turning back at Ebisu would have disrupted Narita Express and Shonan-Shinjuku Line trains on the freight line.
In July 2001, JR introduced a women-only car on late-night trains leaving Shinjuku. It was the first women-only car on a commuter-type train on JR lines. In August 2001 a six-door car was tested in one train. On 1 December 2002 the line was extended to Ōsaki. At the same time it began through running with the Tokyo Rinkai Rapid Transit Rinkai Line (りんかい線), which had just been extended from Tennōzu Isle to Ōsaki. Trips from Shinjuku to Tokyo Teleport took about 23 minutes, and from Shibuya about 17 minutes. From 2002, six-door cars were added to the line in place of ordinary cars, mostly from the Yamanote Line. By 2008 most sets had one, placed in cars 2 and 3, the most crowded. In April 2005 women-only cars were set for the morning rush, the first time on JR East. In July 2005 the Tokyo area train management system (ATOS) was installed at all stations on the line. In March 2006 women-only cars were also set on through trains from the Rinkai Line.
On 28 December 2009 a security camera was installed in car 1 of one 205 series train. On 14 March 2011 Tokyo Electric Power carried out planned blackouts, and through running with the Kawagoe Line and the Rinkai Line was stopped for the whole day. From 30 June 2013, E233 7000 series trains replaced the 205 series, and a few 205 series trains were kept as spares for the ATACS work. From August 2016 the line began station numbering. On 27 October 2016 the 205 series workings ended, so the 10-car 205 series trains were gone. On 4 November 2017 the ATC-6 signalling on the Ikebukuro to Ōmiya section was replaced by ATACS.
On 1 April 2018, after Uzui station on the Sanko Line closed, Kita-Toda station on this line became the highest elevated station in Japan. On 30 November 2019 through running with the Sotetsu Line (相鉄線) began. The Sotetsu-JR through line runs from Shinjuku to Hazawa Yokohama Kokudai and Ebina. Between Shinjuku and Ōsaki, Sotetsu trains share track with the Saikyō Line and the Shonan-Shinjuku Line. Sotetsu trains use the same E233 7000 series trains as the Saikyō Line, so passenger information shows them as Saikyō Line services. The same timetable change added rapid stops at Naka-Urawa, Minami-Yono and Kita-Yono. Between Musashi-Urawa and Ōmiya, the rapid trains now stop at every station and fewer local trains run. The trip took 3 minutes longer. The longest gap between trains went from 16 minutes to 10 minutes. JR East said the change made the timetable more regular. Reports also point to the need for more trains and crew for the Sotetsu link. Saitama City council passed a resolution criticising the cuts and asking for more trains at rush hour. On 1 July 2026 JR East changed from a branch system to business headquarters. The Ōsaki to Shibuya section moved to the Shibuya Business Headquarters, the Shinjuku area to the Shinjuku Headquarters, and Ikebukuro to Ukifunatsuwatari to the Ikebukuro Headquarters. The Ōmiya branch area moved to the Ōmiya Headquarters, with station duties at Musashi-Urawa under the Musashino Headquarters.
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Written by an AI from the line's history on Japanese Wikipedia, nothing else, and checked by a program for dates and numbers that are not in those facts. It can still be wrong. Adapted from Japanese Wikipedia, CC BY-SA 4.0; this text is shared under the same licence.